This invention relates to a process for the separation of cyclohexene and more particularly to a process for separating cyclohexene from a feed which contains a mixture of cyclohexene and cyclohexane, selectively by adsorptive separation techniques.
Cyclohexene is one of cyclic unsaturated hydrocarbons useful as starting materials for manufacture of organic compounds such as cyclohexanol and adipic acid. Generally, cyclohexene is prepared by a selective partial hydrogenation of benzene or a selective dehydrogenation or oxidative dehydrogenation of cyclohexane. In this case, the reaction product is obtained as a mixture (hereinafter referred to simply as the "reaction mixture") containing benzene, cyclohexene, and cyclohexane. Therefore, in order to obtain cyclohexene advantageously on an industrial scale, the separating and purifying operation for the reaction mixture is important. There has been proposed a method of separating, by the adsorption technique, cyclohexene from the reaction mixture after separation of benzene, namely a mixture scarcely containing benzene and consisting essentially of cyclohexene and cyclohexane. This method employs zeolite as an adsorbent and also employs as a displacer or developer at least one member selected from the group consisting of olefinic hydrocarbons, halogenated aliphatic hydrocarbons, ethers and carbon disulfide (see Japanese Published Unexamined Patent Application No. 64530/1980).
According to this method, however, the displacer or developer deteriorates easily because it is chemically unstable, so it is unpreferrable to reuse it by recycle. Therefore it is difficult to employ as an industrial method. Besides, such deterioration of the displacer or developer causes degradation of the adsorptive capability of the adsorbent, so that it becomes impossible to separate cyclohexene in sufficiently high purity. Furthermore, a regenerative treatment is often required to recover the adsorptive capability of the adsorbent, and this has been an operational problem. When low boiling compounds are used as the displacer or developer, a special care is required in handling it and the working efficiency slows down.
It is an object of this invention to provide a new desorbent for cyclohexene which is chemically stable and does not deteriorate, and which can be easily and effectively separated from the mixture of cyclohexene and the desorbent with a distillation method.
It is another object of this invention to provide an effective industrial process for the separation of cyclohexene.
It is a further object of this invention to provide a process for the separation of cyclohexene whereby cyclohexene can be separated in high purity without deterioration in the performance of an adsorbent.
It is a still further object of this invention to provide a part of the method of separating and recovering each component from the reaction mixture which is obtained by a manufacturing method for cyclohexene.
Other objects and advantages of this invention will become apparent from the following description.